1. Field of the Invention
The invention relates to a device for diagnosing malfunction in a fuel tank.
2. Description of the Related Art
In order to prevent fuel vapor produced in a fuel tank from being discharged to the atmosphere, in a known engine, a charcoal canister containing activated carbon is provided. The vapor in a space above the surface of the fuel stored in the tank is introduced into the canister and is adsorbed on the activated carbon thereof. A large amount of the vapor, introduced into the canister, needs a large canister. Therefore, it is preferable to minimize the amount of the vapor produced in the tank in order to reduce the size of the canister.
In order to minimize the amount of vapor produced in the tank, a fuel tank which comprises a fuel-impermeable separator film in an interior of the tank, as disclosed in Japanese Unexamined Utility Model Publication No. 60-158923, has been developed. The film is in contact with the surface of the fuel in the tank to reduce the space above the fuel surface and moves up and down with the movement of the fuel surface. The small space above the fuel surface leads to a smaller amount of vapor being produced in the tank.
In the tank described above, the amount of vapor may increase if the film has problems, such as holes formed in the film, or if the film cannot move up and down as the fuel surface moves up and down. Therefore, it is necessary to diagnose the malfunction in the tank and to warn the driver of the vehicle.
Therefore, the object of the invention is to provide a device for diagnosing malfunction in the fuel tank of a vehicle.